Submission #957280

#	Time	Username	Problem	Language	Result	Execution time	Memory
957280		duckindog	Aliens (IOI16_aliens)	C++17	4 / 100	1 ms	600 KiB

aliens

#include <bits/stdc++.h>

using namespace std;

#ifndef LOCAL
#include "aliens.h"
#endif

struct Line { 
  long long a, b;
  double x(const auto& rhs) { return 1.0 * (rhs.b - b) / (a - rhs.a); };
};

long long take_photos(int n, int m, int k, vector<int> r, vector<int> c) { 
  using pii = pair<int, int>;
  vector<pii> p(n);

  for (int i = 0; i < n; ++i) {
    if (r[i] > c[i]) swap(r[i], c[i]);
    p[i] = {r[i], c[i]};
  }

  auto dis = [&](pii a) { return abs(a.first - a.second) + 1; };
  
  sort(p.begin(), p.end(), [&](const auto& a, const auto& b) { return dis(a) < dis(b); });
  vector<bool> mk(n, true);
  for (int i = 0; i < n; ++i) { 
    if (!mk[i]) continue;
    for (int j = 0; j < i; ++j) if (mk[j] && j != i) { 
      if (p[i].first <= p[j].first && p[j].second <= p[i].second) mk[j] = false;
    }
  }
  int cnt = 0;
  for (int i = 0; i < n; ++i) { 
    cnt += mk[i];
    if (mk[i]) p.push_back(p[i]);
  }
  p.erase(p.begin(), p.begin() + n);
  p.push_back({-1, -1});
  k = min(k, n = cnt);
  vector<vector<long long>> f(k + 1, vector<long long>(n + 1, 1e15));
  sort(p.begin(), p.end(), [&](const auto& a, const auto& b) { return a.first < b.first; });

  f[0][0] = 0;
  for (int i = 1; i <= k; ++i) {
    vector<Line> hull;
    for (int j = 1; j <= n; ++j) {
      
      int pl = -p[j].first + 1;
      long long pre = max(0, p[j - 1].second + pl); pre *= pre;
      Line line = {2 * pl, f[i - 1][j - 1] + pl * pl - pre};
      while (hull.size() > 1 && hull.end()[-2].x(hull.end()[-1]) < hull.end()[-2].x(line)) 
        hull.pop_back();
      hull.push_back(line);
    
      auto cal = [&](int it) { 
        const auto& [a, b] = hull[it];
        long long x = p[j].second;
        return a * x + b + x * x;
      };

      int l = 0, r = hull.size() - 2, it = 0;
      while (l <= r) { 
        int mid = l + r >> 1;
        if (cal(mid) >= cal(mid + 1)) l = it = mid + 1;
        else r = mid - 1;
      }
      f[i][j] = cal(it);
      
    }
  }
  return f[k][n];
}

#ifdef LOCAL
int32_t main() { 
  cin.tie(0)->sync_with_stdio(0);

  int n, m, k; cin >> n >> m >> k;
  vector<int> r(n), c(n);
  for (int i = 0; i < n; ++i) cin >> r[i] >> c[i];

  cout << take_photos(n, m, k, r, c) << "\n";
}
#endif

Compilation message (stderr)

aliens.cpp:11:18: warning: use of 'auto' in parameter declaration only available with '-fconcepts-ts'
   11 |   double x(const auto& rhs) { return 1.0 * (rhs.b - b) / (a - rhs.a); };
      |                  ^~~~
aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:64:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   64 |         int mid = l + r >> 1;
      |                   ~~^~~

• Subtask 1: 4 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40